The present invention generally relates to an apparatus and a method for resolving an ambiguity from a direction of arrival estimate. Further embodiments of the present invention relate to enhancing ambiguous spatial audio parameter estimation.
The present invention is settled in the context of spatial audio coding with a microphone front-end. We focus on parametric techniques, i.e., spatial sound is described by means of one or more audio signals accompanied with parametric side information. The side information is obtained on the basis of at least two microphones. Microphone arrangements and signal processing architectures are usually designed to cover a certain frequency range of interest, where desired specifications are strictly met. Beyond this area of interest notable deviations from the necessitated spatial selectivity might occur. An extreme deviation consists of so-called spatial aliasing. In the context of sound field analysis, the most important effect of spatial aliasing is that estimates of the direction of arrival of sound become ambiguous. Consequently, a certain behavior, which is expected or desired for only one certain direction, is also observed at one or more other directions.
The purpose of spatial audio coding consists of reproducing spatial acoustic scenes by means of few audio channels accompanied with parametric side information. Consequently, a general problem is that inaccurate parameter estimates will cause undesired results of the reproduction procedure or any other processing unit (e.g., for directional filtering), which makes use of the spatial parameters. This consideration applies to the above mentioned affected frequency ranges, especially where spatial aliasing occurs.